Abstract
This paper introduces a spindle-integrated 3-axis force sensor consisted of 2-axis curved-edge sensor (CES) for the radial direction and single axis capacitive sensor (CS) for the axial direction. The proposed single unit force sensor was used to monitor the carbon fiber-reinforced plastic (CFRP) milling and drilling processes and to understand their machining mechanics. Unlike a conventional cutting force sensor can non-contact measure the displacement of the spindle and estimate the cutting force by multiplying the spindle stiffness and the measured displacement. The force sensor unit was successfully integrated with the spindle and measured the cutting force while machining the CFRP plates with 0°, 45° and 90° fiber orientation. The conventional 3-axis force sensor was also used for a baseline comparison with the cutting force results measured by the proposed method. To monitor and characterize the delamination effect of CFRP, the time-frequency domain scalogram images analyzed form the cutting force data were used. Unique features were extracted according to the fact of existence and nonexistence of the delamination. Laser, the sensor measured capability, allowing for in-process CFRP machining process monitoring and CFRP defect mode prediction was discussed.
